Model Engine Gallery Page 17

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This pair of Cox TD 09 Diesels is the work of Jon Fletcher (OZ). Jon lapped the bores to reduce taper to that acceptable for a diesel. That meant a new piston and conrod assembly. His first attempt used press fit spacers either side of the conrod up inside the piston but after bursting a piston on assembly, Jon changed to wire circlips made from 0.012" diameter piano wire as gudgeon pin retainers. Influenced by Alan Allbon designs, Jon set the pin low in the piston to give a good compression seal. The gudgeon pin is 0.1250" dia. drilled out at either end. The total reciprocating weight actually ended up less than that of the TD 09's hardened piston and ball joint little end.
Jon found he had to fabricate some copper sealing washers out of copper bar 0.008" thick to get a leak free joint between button insert and cylinder internal face.
He also had to sleeve the venturis down from 0.133" dia. to 0.106" as the big glow
venturi required the needle to be 6-1/2 turns open and raw fuel could be seen
going down the inlet when running flat out. Unsurprisingly, the engines had an enormous thirst.
With the smaller venturi, the needle position is about 3 turns open.

The engines are very easy to start and go almost as hard as the glow versions
n standard diesel mix as the glow version does
running 30% nitro. After running in and using contest diesel fuel, Jon expects they will
equal or exceed the glows performance.

This little diesel is one of a pair built by Richard Fellas (NZ) based on the 0.5cc DC Dart. It has a bore of 9.0mm and a stroke of about 9mm (the second one has a stroke of 9.4mm), so the displacement is approaching 0.6cc. Wanting a name for it rather catchier than "Richards 0.5 diesel", and observing that there seems to be a long tradition of calling small engines after insects of the buzzing kind, so Richard cast around for something appropriate and came up with a name from the Kiwi perspective, the Sandfly. This was especially apt as some of the thinking behind the engine's genesis was done in PNG where sand flies have been known to exist too (Richard, like most Kiwis and Ozzies, is fond of understatement). The engine was built on an ancient Myford ML7 and an original Unimat. For those interested in small diesels, Richard has generously offered plans and some build notes for the Sandfly, which we'll set free in 2013.

The Weaver 1cc diesel was the basis for this 0.43cc "mini Weaver". It was made by Dave Miner (USA) using wire EDM to produce a crankcase blank (see MEN, August 2010). Dave chose a bore of 0.312", and a stroke of 0.366". He simplified the rather intricate Weaver transfer porting scheme to a single Cox-like port at the front of the cylinder. Running was initially a problem. The engine would fire, then oscillate forward-backward around TDC. This behavior is not uncommon on small diesels. The causes and cures are various. In Dave's case, it was a way too rich mixture. With that sorted, the engine turns a 5-1/2x3 prop at 10,300 rpm, dropping to 9,550 on a 6x3. Dave wrote that his final timing numbers were inlet 90°, transfer 100°, and exhaust 130°. These are about ideal for piston ported engines.

As we saw on page 16, Tug Wilson likes taking a well known (and loved) commercial design of days gone by, and producing 5cc versions of it. This time, her's enlarged the 1957 Super Tigre G32 1cc diesel to 5cc, using just experience, enginuity, and hard work—despite appearances, no castings, nor CNC, EDM, etc are used, though Tug does have have his cases bead blasted. Tug sent a number of photos, all of which are just too drool-worthy not to pass on, so follow this link to more G32 "Big Tigre" pictures..

These photos show the work of Warren Vickery (UK), a home-built Wankel rotary built by him in 2010. The engine has an effective capacity of 7.2cc and uses glow plug ignition. Warren designed and built the engine over a period of several months, and reports that like all good engine projects, the tooling (and machinery...) required to build the engine took more effort and time to manufacture than the engine itself!

The main machines used were a homemade CNC milling machine and a manual bench-top lathe. Previously, Warren had built a 0.8cc 2 stroke CI engine of his own design and says that achieving the required tolerances on that small CI engine was a doddle in comparison to the Wankel. Having said that, the Wankel started on the second attempt and runs remarkably well and is the smoothest model engine that he has run, with almost no vibration across the speed range. It is also one of the thirstier model engines that Warren has run! Performance wise, the engine will turn 12,000 rpm with an APC 11x6 propeller, while 11,200-11,500 rpm is more typical at a slightly richer setting.

For the technically minded, the engine uses apex seals only made of grey iron. Like the commercial OS Wankel, no side seals are used, depending on a close sliding fit (0.007mm) to seal the rotor.

I always get a big kick out of photos sent in by readers which have been built to plans I've drawn up over the years. This Series 1 Mills 1.3 is the work of Jim Frew (UK), from my plans and build article which appeared in Volume 1, Issue 1 of Model Engine Builder magazine (back issues still available).

While building the engine, Jim found need to use a technique for growing cast iron, as described in the Prototype Taplin Twin page, to fix a slight problem with his pistons. This worked a treat and Jim reports that the engine runs well—the camera shutter has "stopped" the 9x4 prop, but you can see some smoke and the appropriate gunge emerging from the exhaust in the running photo.

This engine is the fine work of Jan Huning (UK). Jan was inspired by a photo on this web site of a rear-induction Oliver Cub. In that piece, I discussed possible ways of achieving correct alignment for a screw-in backplate which incorporates the venturi inlet. Jan wrote that the methods for manufacture were a challenge snd prompted him to search for another method. Luckly, sometime back Jan had been given a genuine Oliver unmachined crankcase casting casting. He machined the inlet stub off, and used a friend's bead blaster to give it a similar finish to the rest of the cast surface. The internals were copied from an original Mk 4.

The final way chosen of machining the backplate with no trial and error was perhaps a little long winded, so unsuited to quantity production, but frine for a one-off. The crankcase was completely finished first and then the backplate started. The thread, flange and bore were all completed at one setting, with a large lump left on what would be the outer end. This was then screwed tightly into the crankcase, loosening and tightening a few times to bed the threads. The crankcase was bolted to a jig, at an angle of 45#° to machine the inlet hole and start profiling the outside (a bolt was also put through backplate and crankcase as an additional clamp to ensure the backplate did not start to unscrew during the milling, which would be a little irritating...) The part machined backplate was then removed and held in a split threaded bush in a chuck on the rotary table for the rest of the machining.

Following my ramblings, Jan elected to use no gasket between backplate and crankcase, as with a 32 tpi thread even half a thou of additional gasket compression would result in a rotation of 6°.

Jan reports that the engine runs nicely and seems to have a similar performance to his original Mk 4. The crankshaft and cylinder are not hardened, but they are high strength low alloy steel (EN16M, supplied in the 'T' strength condition). The engine was the engine again at the autum 2011 Old Warden flying weekend, performing faultlessly.

This Gotham Hobby Deezil replica is the work of prolific Ozzie engine builder, Rob Jenkins (Sydney, Autralia). Like many others all around the world, it was made from one of the late Roger Schroeder's casting kits. As you will read if you follow the first link, the Deezil gained a rightly justified reputation for being just about un-runnable, but this was due to the quality of the manufacture and fits, the base design is quite sound. So sound in fact that a well built Deezil will out perform the much vaunted ED Competition Special!

Rob's copy is no exception. In the last photo we see it swinging a 10x6 prop, probably a "Master Airscrew" from the white tracks visible in the spinning prop arc. Rob reports that the engine starts really easily and is not sensitive on any of the controls, though his contrapiston is a bit on the tight side—a better position to be in than one that is a bit loose!

The finish on the case is "as cast". Roger freely admitted that the surface of his castings were less than glassy smooth, being cast is simple green sand in his basement. A clay bonded sand like "Petrobond" can deliver a sand casting almost as smooth as a gravity die casting. Roger tried it once but found the downside was the smell the petrobond gave off, which being in the basement, soom permiated the house, resulting in a ban from Barbera, so back to green sand and the consequent rough finish. Rob is still deciding on whether to polish up the case. Leave it as is, Rob—pure Schroeder original!

In August 2009, Jim Frew (Dorset, UK) completed his first 0.46cc Mk II ED Baby replica to Model Engine News plans and Roger Schroeder's casting kit. His engine started easily and ran well, so Jim emailed Roger asking for another crankcase casting, thinking to make a Mk I version from it. Knowing from experience just how tricky it is to make small diesels, Roger replied saying, "In recognition of your achievement in getting an ED Baby to run I will send you another c/case casting at no charge!" This was typical of Roger who wanted to encourage engine makers more than make a doller from his casting kits.

In fact, it was Roger's Deezil kit which got Jim started making model engines in the first place. Jim's second Baby had a long gestation, being completed in August 2011. The most obvious difference is the "port hole" exhaust openings around the base of the cylinder jacket (inside, the liner still has three slits like the Mk II). While this arrangement makes for a stronger jacket, the holes tend to hold fuel in a maniscus which makes the engine easier to flood than its successor, but as we see here, Jim's version runs just fine—after the settings and "tricks" of the engine have been sorted.

Take special note of the green fuel tank. The idea for these came from Motor Boy, Bert Streigler (TX USA): take one appropriate sized screwdriver with a colored plastic handle; remove the bits that don't look like a fuel tank, then fit to engine. Jim has a local market with a stall that sells used fuel tanks "in the raw" for 10 shillings.

This is the sort of story that I really like, a total basket case restored to running condition. Jim Frew (UK) managed to win an ED Hornet case, backplate and cylinder assembly. He dropped me an email asking for guidance in guessing the conrod length which, by coincidence, I'd already worked out (and later verified) when restoring a Hornet with a broken rod. As Jim progressed, another mail arrived asking for the cylinder fin width and spacing, so another little CAD drawing was made and sent off. The result is as you see here and more than rewards me for any time making those drawings. Here's what Jim had to say about the restoration.

The ED Hornet is now restored, thanks again for your help with this Ron. Removing the guess-work from this project helped to make progress much easier, although there were still plenty of stuff-ups which created twice as much swarf than I intended.

The crankcase, backplate and cylinder appeared on eBay and thinking it might be worth a try to restore it, I had a go and won it for about £15.00. I repairing the broken lug on the crankcase using Thechno Weld. Just file the broken edges then tin both parts, hold together and heat to temperature. Allow to cool then mill off excess material and use a Swiss file to match to the profile of the lug. The unbushed crankcase bearing was a mess so I fitted a bronze bearing. The crankshaft and a HE15 high strength aluminium con-rod as you suggested was made with no problems.

The cylinder/piston assy was stuck solid with the piston halfway up the liner, fortunately there was a thread in the contra so I was able to pull out the contra and then push out the piston from above. After cleaning it was found to still be a good fit and the compression turned out to be good as well.

Making the cylinder head I used the same procedure you describe for the ED Baby. All went well until the final op to machine the flats on the top of the head, I made a threaded plug so that the head could be held in the rotary table and used a strap wrench to make it tight. Then proceeded to mill the flats on the top of the head. All was going well, then just before taking the last few thou the head started to unscrew, this happened so fast I was unable to stop the mill in time before the 3/8" end-mill had chewed into the top of the head and the upper fins.

Started making another head again only this time I was going to machine the flats before parting off, so milling from the side instead from above using a 1/4" end mill. This worked out fine and parted off the head intact. Whew!!!

The backplate cleaned up in the lathe and the fuel system is the same as the ED Bee.

The engine started after a few flicks once the settings were found. I see what you mean about the noise this engine makes, as you mentioned in Engine Findernot a neighbourhood friendly engine.

This four-stroke is the work of Ian Munro (NZ).
It is based around the old open rocker Enya FS but has a single camshaft. Enya gears were used to index the cutting of shop-made gears for the engine. The gears, valves, crankshaft and cylinder liner are all 4140 nitride hardened steel. The piston is lapped cast iron, but Ian intends to replace this wit a ringed piston some time in the future.

The crankshaft and pinion drive are ball-raced, the same as Enya. The cams are surface hardened steel and are pinned to the cam drive spur gear. Aluminium parts are made from 6061 alloy, while the conrod is 7075 alumnum, bronze bushed. Ian reports that the engine is a good runner, turning a 12 in prop at 8,500 rpm and refers us to this this Youtube video of the engine being bench run. He also likes to fly the engines he makes, so the four-stroke will get some limited air time in a vintage model at some stage.

This Mills P.75 was built by Jim Frew (UK) from one of the late Roger J SchroeterClassic Engine kits and plans, serial number 175. Perhaps noticing the "USA" cast into the backplate, Jim used all American threads on his engine. He reports it runs just like a Mills should, and the only problem is a slight warping down—not that you'd ever notice—of the fins due to insufficient rake on one side of his fin cutting tool causing friction and heat deformation. It was precisely this problem on my first Schroeder kit—the Original Ohlsson, that made me pull the Quorn castings out from under the bench and embark on a nine month odessey. Still, good job Jim, Roger would be tickled pink.